Certain 3-phenoxybenzyl esters of cyclopropanecarboxylic acids and of .alpha.-isopropylphenylacetic acids are generally referred to as "pyrethroids", being characterized by the common properties of rapid action on insects, i.e., they are "quick knockdown agents", and low mammalian toxicity. However, while such compounds are desirable insecticides, they tend to be difficult and expensive to manufacture, because of their relatively complex chemical structures. Consequently, it is desirable to minimize the amount of such pyrethroid that is required to control the insects.